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Diffstat (limited to 'Documentation/sysctl/fs.txt')
| -rw-r--r-- | Documentation/sysctl/fs.txt | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt index 8c235b6e4246..88152f214f48 100644 --- a/Documentation/sysctl/fs.txt +++ b/Documentation/sysctl/fs.txt @@ -32,6 +32,8 @@ Currently, these files are in /proc/sys/fs: - nr_open - overflowuid - overflowgid +- protected_hardlinks +- protected_symlinks - suid_dumpable - super-max - super-nr @@ -157,6 +159,46 @@ The default is 65534. ============================================================== +protected_hardlinks: + +A long-standing class of security issues is the hardlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like /tmp. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given hardlink (i.e. a +root process follows a hardlink created by another user). Additionally, +on systems without separated partitions, this stops unauthorized users +from "pinning" vulnerable setuid/setgid files against being upgraded by +the administrator, or linking to special files. + +When set to "0", hardlink creation behavior is unrestricted. + +When set to "1" hardlinks cannot be created by users if they do not +already own the source file, or do not have read/write access to it. + +This protection is based on the restrictions in Openwall and grsecurity. + +============================================================== + +protected_symlinks: + +A long-standing class of security issues is the symlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like /tmp. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given symlink (i.e. a +root process follows a symlink belonging to another user). For a likely +incomplete list of hundreds of examples across the years, please see: +http://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp + +When set to "0", symlink following behavior is unrestricted. + +When set to "1" symlinks are permitted to be followed only when outside +a sticky world-writable directory, or when the uid of the symlink and +follower match, or when the directory owner matches the symlink's owner. + +This protection is based on the restrictions in Openwall and grsecurity. + +============================================================== + suid_dumpable: This value can be used to query and set the core dump mode for setuid |
